Light sensitive device



Sept. 3, 1935. H FRlEND 2,013,095

LIGHT SENSITIVE DEVICE Filed Aug. 29, 1951 INVENTOR HALTON H FREND ATTORNEY Patented Sept. 3, 1935 PATENT OFFICE 2,013,095 LIGHT SENSITIVE DEVICE Halton H. Friend, New York, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application August 29,1931, Serial No. 560,126 2 Claims. (Cl. 250-275) This invention relates to light'sensitive devices such as are used in sound picture recording and reproducing apparatus. It has as its principal object the provision of an improved means of 5 shielding such devices from electrostatic or electromagnetic disturbances and the like.

When a light sensitive device such as a photo tube is utilized in connection with a high gain amplifier, noises due to electrostatic and other eX- traneous disturbances are likely to be produced.

These noises are of course amplied by the amplifier and may become very troublesome. It has been attempted to obviate them by the provision of a shield surrounding both the amplifier and 15 the proto-tube. In order for light modulated in accordance with sound to enter the tube it is necessary that an opening be provided in the shield. It has been found that such an opening prevents satisfactory elimination of the distur- 20 bances. In accordance with the present invention the light sensitive tube is completely enclosed by a close fitting shield, a perforated section for the passage of light being arranged to cover the tube window. Such a shield is electrostatically 25 opaque and optically transparent.

. The invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims. 30 Referring to the drawing:

Fig. 1 is a side view of a light sensitive tube constructed in accordance with. the invention, and Fig. 2 is a sectional view taken from the section 2----! of Fig. 1. 35 Fig. 3 is a view from the bottom of Fig. 1.

The device includes a glass container II] mounted on a metal base I3 which is surrounded by a shield H of electrolytically deposited ,copper or the like. A window I5 in the shield I I is covered by a shield I2 which may consist of wire mesh :5

sulation I6 extending through the metal base I3. 10 I It is preferable that the shield I I contact with the base I3 and that the whole shielding system be grounded. Since the photo-tube is completely enclosed by'the grounded electrostatically opaque shield disturbances due to stray fields are completely eliminated. It has been found that the perforated portion of the shield which covers the window is optically transparent and has substantially no effect on the modulated light applied to the tube. The shield does not require extra room and permits ready use of the tube in the. limited space commonly available in sound recorders and sound reproducers.

I claim:

1. An electrostatically opaque shield for a light sensitive tube including an electrically conductive envelope provided with an opening, and a wire mesh covering said opening.

2. Anelectrostatically opaque shield for a light sensitive tube including an electrically conductive envelope provided with an opening, and an electrically conductive mesh covering said open-' mg.

HALTON H. FRIEND. 

